Apparatus for preheating printed circuit boards

Claim 1

In combination, heating means having a flat horizontal upwardly facing heating surface, a heat transfer device comprising a thermally nonconductive horizontal rigid base plate and a large plurality of elongated thermally-conductive vertical heating elements extending through and upwardly beyond said plate from bottoms of said elements on the underside of said plate to upper tips of said elements all lying in a common horizontal plane above said plate, said elements being fixedly supported in fixed alignment with each other by said plate and being distributed over the horizontal area of said plate so that their tips are arranged in said plane in a two-dimensional pattern of tips uniformly spaced in such pattern from each other, and said device being supported by said heating surface so that the bottoms of said elements abut and are in thermal contact with said surface, and a printed wiring board having electric circuit components on the top thereof and having leads of said components extending through said board to project downwardly beyond the bottom thereof, said board resting on said pattern of heating element tips with the downwardly projecting leads from said board being interspersed with ones of said elements to extend downward in the spaces therebetween so that said pattern of tips supports said board to be level to permit substantially uniform heating of all portions of said board by said elements.